Precision linear Hall sensor for current and position sensing applications
The new A1351 from Allegro MicroSystems Europe is a high-precision linear Hall-effect sensor
IC with a 125 Hz push/pull pulse-width-modulated (PWM) output that is proportional to an applied magnetic field.
The A1351 converts an analogue signal from its internal Hall sensor element to a digitally encoded PWM output signal. The coupled noise immunity of the digitally encoded PWM output is far superior to the noise immunity of an analogue output signal, making the device ideally suited to current and position sensing applications in the automotive and industrial markets.
A BiCMOS monolithic circuit within the A1351 integrates a Hall element, precision temperature-compensating circuitry to reduce the intrinsic sensitivity and offset drift of the Hall element, a small-signal high-gain amplifier, proprietary dynamic offset cancellation circuits, and PWM conversion circuitry.
The dynamic offset cancellation circuitry reduces the residual offset voltage of the Hall element, which is normally caused by device overmoulding, temperature dependencies and thermal stress. The high-frequency offset cancellation (chopping) clock allows for a greater sampling rate, which increases the accuracy of the output signal and results in faster signal processing capability.
The A1351 has customer-programmable offset and sensitivity, with a factory-programmed 0%/degC sensitivity temperature coefficient. Sensitivity is selectable between 0.055% and 0.095% duty cycle per gauss.
Other features include selectable unipolar or bipolar quiescent duty cycles, output duty-cycle clamps to provide short circuit diagnostic capabilities, and an optional 50% DC calibration test mode at device power-up.
The device is resistant to mechanical stress, and operates over a wide ambient temperature range of -40°C to +125°C. It offers temperature-stable quiescent duty cycle output and sensitivity, as well as precise recoverability after temperature cycling.
An internal filter of approximately 50 Hz bandwidth is used to achieve 11 bits of output resolution. A simple RC network can be used to convert the digital PWM signal back to an analogue signal.
Key applications for the A1351 include battery current sensing, exhaust gas return systems, throttle position sensing, and ride height and seat belt tensioning systems.
The A1351 is supplied in a thin (1 mm) 4-lead single-inline package (suffix KT) which is lead (Pb) free, with 100% matt tin leadframe plating.
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